RCBO Testing

[Rumacoai]

Question - Is it me or the equipment ?

I have a 6 amp Wylex RCBO on a lighting circuit that tests OK at the farthest point of circuit and mid way point, but will not test at CU. It will not trip. I am using a Fluke 1654B on Auto.
I have two other RCD's on board that both test at CU ok


I done this due to a post in another forum, and I was interested to see the outcome.


Are there any reasons or tricks I am missing.

 

[richy3333]

Not sure why you are testing at furtherest point and mid way, but could you describe what you are doing at the board in more detail? It sounds as though this might be the issue if the RCBO is testing out directly from the circuit?

 

[Rumacoai]

I tested at end and mid way to see if the RCBO would work at all, curious I suppose

Using croc clip on Earth bar, then test probe on supply entry point

I have tried with load attached and load removed, same result though will not trip, (I am thinking new RCBO)

 

[Guest123]

Using croc clip on Earth bar, then test probe on supply entry point

Sorry, can you clarify exactly where you placed the probes on the RCBO?

 

[Rumacoai]

Sorry wasn't clear was it, I will try again

Test lead and probe to contact nearest to bus bar at the bottom of RCBO,

Like the poppy, I use to dislike FIFA now despise them !

cheers

 

[Guest123]

Sorry wasn't clear was it, I will try again

Test lead and probe to contact nearest to bus bar at the bottom of RCBO

Thats why it wont trip then, you need to place the probes on the LOAD side of the RCBO, where the outgoing circuit cables are connected.

 

[Rumacoai]

Will try that tomorrow and let you know how it goes

Thanks for the help

cheers

 

[Rumacoai]

It Transpires my probe was not long enough to contact with supply line. All sorted now. cheers for help

 

[ian65]

Hi there RCBO testing was a question in the Oct 20th 2391 exam and thats why i am looking around for answers.

Just come across this thread and it looks like it will help me understand "How to testa RCBO".

Many thanks Ian.

 

[WDMDL]

Exactly the same way as you'd test an RCD: 0.5Idn (no trip within 2 sec), Idn 0deg, Idn 180deg, 5Idn 0deg, 5idn 180deg.
As mentioned, you may need a long, thin probe to make a connection to the Neutral out terminal of the RCBO, as they are recessed by 25-30mm or so on most types.

Also, you need to disconnect the outgoing circuit when performing insulation resistance tests on it. The disconnection is only single pole so the Neutral will go straight through to the busbar.
You should disconnect the Neutral flying lead when testing on the busbar side of the RCBO
Many have a functional earth connection, so this should be disconnected for IR testing too (manufacturer's instructions).

Simon.

 

[Rampage]

Wasn't there another thread on here a few weeks ago about a certain make of RCD's not tripping when tested on the RCD'S rather than at the end of the circuit?

 

[SparkyDips]

had similar problems with the test probe not making contact, therefore not testing properly!!

also as WDMDL mentioned, need to remove outgoing when performing Insulation Tests due to structure of RCBO.

 

[pencilpusher]

Wasn't there another thread on here a few weeks ago about a certain make of RCD's not tripping when tested on the RCD'S rather than at the end of the circuit?

There certainly was. The OP stated he had to attach a short wire to the load side line terminal for it to trip as it would not do so at the terminal.

 

[chopper]

sorry to jump on this thread, but is this thread saying that it is ok to test rcbos at the DB rather then at the end of line, is this same in domestic and industrial i thought we had to go do it at end of line

 

[pencilpusher]

sorry to jump on this thread, but is this thread saying that it is ok to test rcbos at the DB rather then at the end of line, is this same in domestic and industrial i thought we had to go do it at end of line

I always test at the DB unless its a circuit with sockets on it. We are testing that the RCD/RCBO operates within the required times. This, can be determined at the board.